The 1st Division was formed on 18 June 1809, by Lieutenant-General Arthur Wellesley, commander of British forces in Spain and Portugal, for service during the Peninsular War.

[2][4][5] With the end of the Napoleonic Wars, the division became part of the Army of Occupation based in France where it remained until December 1818, when it was disbanded upon the British withdrawal.

[13] With the Armistice of 11 November 1918 ending the First World War, the Allied Powers agreed to occupy the Rhineland as a way to guarantee future reparation payments.

[18][19] It dispatched troops to reinforce the British Army in Ireland during the Irish War of Independence and later to assist in the occupation of Constantinople.

This saw each brigade decreased from four to three battalions, anti-tank companies added, and saw the arrival of Universal Carriers and more transport to make the infantry more mobile.

[31] In May, Alexander joined high ranking British officers who were dispatched to France to undertake staff talks with their French counterparts.

David Fraser, a historian and former British general, wrote that the regular formations of the BEF were well-trained in small arms, but lacked tactical skill.

Though mobile, the formations lacked specialist weapons, ammunition, spare parts, and communication equipment because of the budget cuts of the inter-war period.

[39] Three days later, with the majority of the BEF now bound within a closing perimeter on the French coast and lacking the ability to hold the position, the decision was made to evacuate from Dunkirk, the only remaining port in British hands.

On 31 May/1 June, they were heavily attacked; some positions were retained while others were breached and the troops forced back to the Canal des Chats.

From its return from France, the division was seen as one of the better equipped and trained formations based in the UK, and was held in a reserve role to be rushed to southern England in the event of a German invasion.

[52] Generaloberst Hans-Jürgen von Arnim, commander of the Axis Panzer Army Africa, was aware that Allied forces were intending to launch a major offensive.

While the German assault caused a potentially dangerous situation to arise for artillery that had been moved forward in preparation for the Allied offensive, it was repulsed with just 106 casualties among the 1st Division.

Initial success was thwarted by the inability to dig in and construct defensive fighting positions and a swift German counterattack.

By 1943, it was garrisoned by 12,000 troops (five untried battalions supported by militia), contained radar sites that could track movement from North Africa towards Italy, and included an airbase with underground hangars.

To avoid the need for a bloody assault, which would be conducted by the 1st Infantry Division, the island was subjected to a heavy aerial bombardment.

[60][61] Unbeknown to the Italian garrison, the ships carrying the 1st Division arrived 8 miles (13 km) offshore on the morning of 11 June.

Around the same time, the ranking members of the Italian garrison held a conference where they acknowledged their situation was untenable and made the decision to surrender.

Under the cover of fighters, a final bombing raid, and naval gunfire, the 1st Division came ashore around noon and were greeted by white flags.

This lasted until early December 1943, when it was transferred to Italy and concentrated near Cerignola in preparation to join the Eighth Army fighting on the east coast of the country.

From late September onwards, consideration for an amphibious landing behind the front line were made, but logistical and strategical constraints delayed such a venture from gaining traction until the end of the year.

The Fifth Army, fighting on the west coast of Italy, was assigned the dual task of advancing north through the Winter Line and conducting the landing.

On 24 January, the division was relieved of its reserve duties and its forward patrols reached Aprilia (nicknamed 'the factory' by the advancing troops) as well as positions along the Moletta River to secure the left flank of the landing zone.

Over the course of the following days, patrols were conducted, minor tactical gains were made, and the division fended off several further German counterattacks that saw at least one British company overrun.

[69][70][71] While the initial corps-wide attack had failed, a renewed effort began on 30 January after sufficient forces had landed and the corps had secured its logistical base.

While the division reached Campoleone, it was unable to push beyond, and the US tanks failed to make their own impact due to mud and terrain limitations.

By the end of 4 February, the German assault had forced the division back to the positions held on 30 January and had inflicted 1,400 casualties.

[82] Operation Diadem was the final battle for Monte Cassino the plan was the U.S. II Corps on the left would attack up the coast along the line of Route 7 towards Rome.

In October of that year, as British forces pulled out of Egypt outside of the Suez Canal Zone, the division garrisoned that area.

[88] When the Cold War ended, the British government restructured the army as part of Options for Change and this saw the division again disbanded on 31 December 1992.